This invention relates to a data transmission system, especially for use where such transmission is needed between a number of closely-spaced terminals or nodes. Such a system may be a fairly large computer installation.
According to the invention, there is provided a data transmission system, which includes a number of similar user nodes interconnected by a multi-conductor bus, impedance terminations at each of the two ends of the bus, and a clock and synchronisation pulse source included at the mid-point of the bus, the pulses generated by the source being propagated in both directions from the source to the nodes served by the system, wherein all control of the system is vested in the user nodes, so that the system does not have a central control arrangement, wherein data is conveyed in time division multiplex (TDM) manner with each time slot available when free for use by any one of the nodes, and wherein each said node includes circuitry responsive to the clock and synchronisation pulse signals to ensure that the nodes are in synchronism with each other.